1. Field of the Invention
The present invention relates generally to coupling systems for transmitting mechanical power between a motor or other prime mover and a driven machine. More particularly, the invention relates to a elastomeric coupling system permitting a certain degree of misalignment between driving and driven shafts, which is easy to install and which provides enhanced retaining forces for an elastomeric element disposed between the shafts.
2. Description of the Related Art
A great number of applications exist for rotating machinery including a prime mover or driver coupled to a driven piece of machinery. In many industrial and other applications, such prime movers include electric motors, hydraulic motors, pneumatic motors, internal combustion engines and so forth. These prime movers are commonly used to drive pumps, conveyers, agitators, fans, as well as a great variety of other machines.
In general, such systems may transmit power from the prime mover to the driven shaft in a variety of ways. For example, direct couplings may be interposed between the shafts, aligning the shafts axially with one another for direct transmission of rotary motion. Historically, fairly rigid couplings required that the shafts be carefully aligned with one another in order to reduce cyclic loading on both the coupling and the shafts, and on bearing sets supporting the shafts. More modem systems include various types of flexible couplings, generally including elastomeric elements interposed between coupling hardware, which permit some degree of misalignment between the shafts, while effectively transmitting power therebetween. Such flexible couplings also provide some degree of cushioning of torque spikes, and facilitate coupling and uncoupling of the prime mover with the driven shaft.
Various forms of flexible couplings have been proposed and are commercially available. In one known arrangement a tire-like flexible element is interposed between attachment structures supported on each shaft. The attachment structures include a hub or bushing which is secured to the shaft, such as by means of a conventional key or tapered locking bushing arrangement. The hub supports a flanged attachment structure including a peripheral flange that extends in a plane perpendicular to the axis of the shaft. The elastomeric element is annular in shape and is split transversely to allow it to be opened and slipped over a gap between the attachment structures. The elastomeric element includes a peripheral bead on either side which is inserted between each support flange and a retaining flange aligned in axially facing relation to each support flange. The retaining flanges are then tightly secured to the attachment flanges by means of axially-extending bolts. As the entire structure is drawn together, the bead on either side of the elastomeric element is compressed in a direction parallel to the axis of the shafts, producing a retention force between the flanges and the elastomeric element. The retention force, in combination with the coefficient of friction between the elastomeric element and its mounting structures affords an excellent torque-carrying capacity to the coupling assembly. Couplings of this type are commercially available from the Dodge Division of Reliance Electric Industrial Company, under the commercial designation Paraflex.
While such couplings provide excellent performance and conveniently permit some degree of misalignment between the driving and driven shafts, they are not without certain drawbacks. For example, couplings of the type described above may be somewhat difficult to assemble depending upon spacing between the prime mover and the driven machine. In particular, clearances of axially-aligned bolts may be fairly short where the machines are placed close to one another, making the bolts difficult to insert and tighten into their corresponding threaded bores in the coupling flanges. In addition, in certain larger sizes of these couplings the elastomeric power transmission element may be difficult to place between the flanged mounting structures, particularly where clearances between the machines limit the distance the attachment and retaining flanges can be spaced from one another.
Other, somewhat similar flexible coupling arrangements have been proposed and are commercially available. In another known design coupling halves are mountable to hubs by means of radially-extending bolts. Each coupling half includes a molded elastomeric element which extends slightly less than 180.degree. around the axially aligned shafts. Semicircular metallic flanges are bonded to the elastomeric elements and extend in a direction generally parallel to the axis of the shafts. The coupling is installed by securing support hubs on each shaft and then bolting two mutually facing elastomeric element and flange assemblies on either side of the hubs. While the resulting structure is relatively easy to assemble, misalignment between the shafts can result in deformation of the metallic flanges and difficulty in inserting retaining bolts into hubs. Additionally, the entire torque-carrying capacity of the resulting coupling depends upon the integrity of bonds formed between the elastomeric elements and the attachment flanges. Even partial rupture of either the elastomeric elements or the bonds can result in tearing of the elements under stress or, in certain cases, complete detachment of the elastomeric elements from the attachment flanges.
There is a need, therefore, for an improved flexible coupling system which avoids the drawbacks of prior art systems. In particular, there is a need for a system which is both extremely rugged and easy to install, even in applications where spacing between driving and driven components is relatively restricted. Moreover, there is a need for an improved flexible coupling system which transmits torque and power by means of substantial holding forces between system components, and particularly between an elastomeric element and mechanical hardware associated with the driving and driven shafts.